Spatial light modulators (SLM) have a wide range of application areas. Examples are light modulation for dotwise exposure of photosensitive media, various displays, screens and signs and for routing light within the telecommunication industry. Very often, the light modulation is performed in systems which also make use of optical fibers or light guides.
The SLMs can be/have been optimized for the wave length range for which they are used. For instance, some systems exist which are optimized for UV-light while others are optimized for visible light.
Basically, there are two types of SLMs—reflective and transmissive modulators. Over the past year or so, a lot of work has been dedicated to designing and fabricating such SLMs using micro-opto-electro-mechanical systems (MOEMS) technology.
Reflective SLMs made in MOEMS technology are often based on arrays of tiny mirrors which can route and/or switch on and off the light by tilting the mirrors into well-defined positions. TI is leading in this area with their DLP-technology which has been—and is being—developed for high definition television (HDTV), digital projectors, home cinemas and a number of other applications. Today they hold a leading position as supplier of optical engines for digital projectors. However, other reflective technologies also exist such as the grating light valve (GLV) technology from Silicon Light Machines in California.
In the telecom industry, reflective systems are also the dominating technology, since this technology is used for routing optical signals between a large number of optical fibers/channels in optical cross fields. By using a reflective technology, such routing can be performed with minimal signal loss. Almost all major telecom suppliers are dedicating a lot of effort—internally or in cooperation with partners—to development and manufacture of such optical routers.
However, for a number of applications, the use of transmissive SLMs is superior compared to the use of reflective systems. There are applications in which a transmissive system for the same light source enables transmission of more light than a reflective system, and there are several applications in which the alignment and assembly of a transmissive system become easier by using a transmissive system instead of a reflective system.
A problem with the prior art MOEMS-based SLMs is that the manufacturing of the modulators involves extreme processes. This problem is especially significant when moving parts, e.g. shutter blades, are built on a wafer substrate.
Further significant problems related to the manufacturing of such SLMs are alignment of the optical system, sealing of the shutter arrangement, component costs, complexity and not to mention physical size.
The invention addresses these problems.